1. Field of the Invention
This invention relates to control systems for machines and the like of the type having at least one cycle made up of at least two events and is more particularly concerned with control systems utilizing momentary switching devices to actuate the machine cycle.
Generally speaking, the control system of the present invention includes a control circuit having momentary switching devices, digital circuitry for latching the control circuit in various modes of operation, and timing circuitry responsive to the digital circuitry for timing at least one of the events of the cycle; and gate circuit means controlled by semiconductor switching devices for regulating at least another event of the cycle in response to the control circuit.
2. Description of the Prior Art
U.S. Pat. Nos. 3,767,937 and 3,973,135 assigned to P. R. Mallory & Co. Inc., disclose control systems which include control circuits having timing means and other circuitry for controlling machines and the like having at least one cycle made up of at least one event. However, these patents disclose the use of pushbutton controls which latch in an on position when pushed or pulled and are then released or latch in an off position in response to a solenoid release. Accordingly, the control circuits as disclosed in the aforementioned patents are latched into at least one operational mode by state of the art mechanical switching devices. Because of cost, reliability and esthetics, it has become desirable to utilize momentary switching devices such as keyboard type switches or electronic touch switches in place of the latching mechanical type switches described above. Since momentary switching devices do not latch, other means must be utilized to latch the control circuit in an operation mode. One such means is to utilize digital circuitry.
Control circuits utilizing momentary switching devices are per se old in the art; as will be recognized by reference to the recently issued U.S. Pat. No. 4,001,599; however, various means may be utilized to implement the momentary signal produced by such switching devices.
Additionally, the timing means associated with control systems such as those disclosed in U.S. Pat. Nos. 3,767,937 and 3,973,135 have generally utilized an oscillator circuit in conjunction with a resistance capacitance timing network in order to provide the timing period for each cycle. Utilization of such timing means has necessitated the use of mechanical switching devices having double contacts i.e. one to latch the control circuit in an operational mode and one to select the appropriate resistance capacitance combination for a desired timing period.
In general, the use of oscillator circuits which produce a series of electrical pulses that are in turn counted in order to derive a timing period for a particular cycle of a machine is old in the art; as will be recognized by reference to U.S. Pat. Nos. 3,774,056 and 4,001,599; however, in most of these instances where counters are used, a time period is predicated solely upon the number of pulses received and/or counted and not upon the frequency of such pulses.
Generally speaking, therefore, the present invention represents an improvement upon the control systems as disclosed in U.S. Pat. Nos. 3,767,937 and 3,973,135 wherein momentary switching devices are utilized and digital circuitry latches a control circuit in at least one mode of operation.